Technical Field
The present disclosure relates to an inverter system. More specifically, the present disclosure relates to an inverter system including a controller for an inverter, by which failure in a high-voltage motor and a high-voltage inverter for driving the motor caused by an erroneous operation of a switch can be prevented, by way of checking an operating state of the switch based on an output current from the high-voltage inverter.
Description of the Related Art
Generally, a high-voltage inverter is an apparatus for controlling an input voltage to a high-voltage motor by adjusting the amplitude and frequency of the voltage input to the high-voltage inverter within the rated voltage of the high-voltage motor.
Such high-voltage motors are commonly installed in major facility of a factory. Since they require very expensive installation cost, a variety of protection apparatus are provided. Specifically, switch gears such as a vacuum circuit breaker (VCB) and a vacuum circuit switch (VCS) are installed between a high-voltage inverter and a high-voltage motor, so that the power is interrupted if an abnormal situation takes place during the operation of the high-voltage motor.
Such switch gears are typically controlled by operating a control panel located in a control room of a factory. A digital contact point is frequently used between the control panel and the switch gear via utility AC power, e.g., AC 220 V.
Although the switch gear is used for protecting the high-voltage motor, sometimes the switch gear itself may be erroneously operated, so that the high-voltage inverter and the high-voltage motor may be damaged. Specifically, erroneous operation due to noise in a control signal sent from the control panel to the switch gear, misfire due to aging of a coil, or misoperation by a user by mistake. As a result, a very big accident may take place. That is, when the switch gear is turned off and immediately turned on during the operation of the high-voltage motor, an overcurrent may occur due to difference in voltage between the high-voltage inverter and the high-voltage motor, so that the high-voltage inverter, the high-voltage motor and the switch gear may be damaged.
FIGS. 1A to 1C are views for illustrating operations of a high-voltage inverter according to the prior art in different operating states.
FIG. 1A shows a high-voltage motor 10 in a normal operating state. When the high-voltage motor 10 is normally operated by a high-voltage inverter 20, the voltage supplied to the high-voltage motor 10 is controlled by the high-voltage inverter 20.
If a switch gear 30 is turned off erroneously while the high-voltage motor 10 is operated, the high-voltage inverter 20 cannot know the operating states of the high-voltage motor 10 and thus keeps outputting voltage, as shown in FIG. 1B. If the switch gear 30 is turned on in this situation as shown in FIG. 1C, the high voltage from the high-voltage inverter 20 is applied to the high-voltage motor 10 instantaneously, such that a failure takes place.
That is, since the high-voltage inverter 20 does not receive a state contact point of the switch gear 30, it cannot know whether the switch gear 30 is turned on or off, and accordingly an accident may occur due to an erroneous operation of the switch gear 30 during the operation of the high-voltage motor 10.